Purpose: To evaluate advantages and disadvantages of identical implants with internal or external connections. Materials and methods: Two hundred patients with any type of edentulism (single tooth, partial and total edentulism) requiring one implant-supported prosthesis were randomly allocated in two equal groups to receive either implants with an external connection (EC) or implants of the same type but with an internal connection (IC) (EZ Plus, MegaGen Implant, Gyeongbuk, South Korea) at seven centres. Due to slight differences in implant design/components, IC implants were platform switched while EC were not. Patients were followed for 1 year after initial loading. Outcome measures were prosthesis/implant failures, any complication, marginal bone level changes and clinician preference assessed by blinded outcome assessors. Results: One hundred and two patients received 173 EC implants and 98 patients received 154 IC implants. Six patients dropped out with 11 EC implants and 3 patients with four IC implants, but all remaining patients were followed up to 1-year post-loading. Two centres did not provide any periapical radiographs. Two prostheses supported by EC implants and one supported by IC implants failed (P = 1.000, difference = -0.01, 95% CI: -0.05 to 0.04). Three EC implants failed in 3 patients versus two IC implants in 1 patient (P = 0.6227, difference = -0.02, 95% CI: -0.07 to 0.03). EC implants were affected by nine complications in 9 patients versus six complications of IC implants in 6 patients (P = 0.5988, difference = -0.02, 95% CI: -0.10 to 0.06). There were no statistically significant differences for prosthesis/implant failures and complications between the implant systems. One year after loading, there were no statistically significant differences in marginal bone level changes between the two groups (difference = 0.24, 95% CI: -0.01 to 0.50, P = 0.0629) and both groups lost bone from implant placement in a statistically significant manner: 0.98 mm for the EC implants and 0.85 mm for the IC implants. Five operators had no preference and two preferred IC implants. Conclusions: Within the limitations given by the difference in neck design and platform switching between EC and IC implants, preliminary short-term data (1-year post-loading) did not show any statistically significant differences between the two connection types, therefore clinicians could choose whichever one they preferred. Keywords: complication, dental implant, external connection, internal connection